Submitted to: Society for Range Management Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: July 18, 2005
Publication Date: February 15, 2006
Citation: Young, J.A., Clements, C.D. 2006. Blue mustard in cheatgrass communities [abstract]. Proceedings Society for Range Management. 58:261-262. February 12-17, 2006, Vancouver, British Columbia. Technical Abstract: Until very recently, the exotic, invasive species of the mustard family (Brassicaceae) that occurred in cheatgrass (Bromus tectorum) communities on former big sagebrush (Artemisia tridentata)/bunchgrass rangelands had yellow or white flowers. In the Great Basin, the “blue” flowered species Chorispora tenella went from a rare botanical curiosity to a landscape characterizing species in a decade. Much of this spread has occurred within the past 3 years. Considerable confusion has existed over identification of the species because a second blue flowered species, African mustard (Malcolmia africana) has spread in the Great Basin during the same time period. Besides flower color and shape, the primary characteristics used to separate annual species of the mustard family are the nature of leaf hairs (lacking, branched or entire), leaf shape (entire of pinnate) and growth form (upright or spreading). Chorispora and Malcolmia have generally entire leaves with few hairs and their growth form can be upright or spreading. Both species vary in all of these characteristics. Flower color for both species is described as ranging from purplish-blue to magenta. Both species are commonly known as blue mustard, but in cheatgrass communities Chorispora is the landscape characterizing species. Even in highly technical aspects of flower structure, the two species are similar. With maturity, the separation becomes obvious. The valves of the fruit (silique) of Chorispora are indehiscent, but breaks in one-seeded segments. The small seeds remain firmly fixed in these segments and germination occurs from within this remnant portion of the fruit. In Malcolmia the seeds disperse from the splitting valves of the fruit. The practical significance of this mustard invasion will become apparent as we understand how it modifies the nature of succession in cheatgrass dominated communities. It has already illustrated how open these communities are to new invasive weeds.